Prior Art
Many fluids, known as non-newtonian fluids, do not have uniform flow properties. These fluids change viscosity depending upon the shear stresses acting on them. The fluids may be less viscous at high flow rates, but increase in viscosity after they have been allowed to set. Therefore, providing a steady state flow of these fluids has long been a problem.
Providing a uniform flow rate of these fluids is often critical. For example, it has become the practice to automatically and continuously load curable polyester resin and a catalyst in distinct compartments formed in a flexible tubular container. These containers of material are produced by forming a continuous length of the dual compartments from a flexible material, loading the polyester resin and catalyst into the separate compartments, and dividing the continuously formed compartments filled with the components into predetermined packages containing the components. These packages are produced on a continuous basis with the polyester resin and the catalyst being injected continuously as the flexible material is formed into the suitable compartments for receiving the material. As many as 1500 such containers are produced per hour.
Although the components are continuously loaded into the compartments of the container, the viscosity of the material may change in response to temperature changes or product consistency. Moreover, because the polyester resin is normally mixed with filler and thixotropic components, the viscosity may vary from production to production. However, in order for each package to be identical in size and firmness, one to the other, an equal volume of material must be loaded into each capsule. Because the container in which the material is loaded is drawn through the process at a constant rate, and severed at constant time intervals, the package itself remains uniform in length. Thus, in order for the final product to be uniform, the pumping system for delivering the polyester resin composition must be capable of producing a uniform quantity of material per unit of time. An irregular supply of the components will result in varying firmness among the packages and thus effect the functionality of the product.
Heretofore, gear pumps and screw pumps have been suggested as appropriate in providing a steady state flow of highly viscous fluids. However, where the fluid viscosity reaches levels of 100,000 centipoise, these types of pumps have been found to be completely unsatisfactory. Both the gear pumps and screw pumps have been found to bind up and fail after very short periods of pumping. Where air driven pumps have been used, they have not by themselves been capable of providing the steady state flow of materials required to produce a uniform product.